RE: getting rid of beaver (trapping beaver)
Water trapping, beaver in particular, is not something you can really throw together overnight and learn on the fly with only a few days to dedicate to the job. In your situation I would suggest hunting the beavers and shooting them with a rimfire like 22lr or 17HMR at close range. Check regulations in your area- since they are furbearers they might be protected. Wintertime trapping would be the best way to affect the population- but for short term relief I would start sniping.